Method of making metal screen stencils



Oct. 2, 1951 H. B. FOWLER 2,569,752

METHOD OF MAKING METAL SCREEN STENCILS Filed July 4, 1945 Tic l.

Patented Oct. 2, 1951 UNITED STATES PAT EN T OFFICE 2,569,752 METHOD OFMAKIN METAL SCREEN STENCILS Harwood B.. Fwler;- Wayne, Pa; Application July 4, 1945, Serial No. 603,175 s elaimsi ('01. 101128.3)

This invention relates to" metal stencils, and particularly to metal screen stencils" through which designs can be applied to an article; and toth'e'methods for forming same. i

For many purposes the conventional sill f screens are too fragile for stencil purposes and have been replaced by metal stencils; a feature of which is a design area comprised of woven" metal fabric joining areas of impervious metal toeffect' the transfer of pigment or paint or the like through the desired areas only. Suchmetal stencils have been found to be fairly accurate and also fairly wear resista'n't, but aspreviousl'y developed have been very complex anddifficult to make. According to' what may be considered the best of the prior art practices in this regard, there was provided a metal screen element of woven wire, with which a contrasting solid metal sheet was intimately associated. The respective metals were so selected that the etchant which would attack one element, say, the solid con firasting sheet of metal, and would eat through or into same to form anetchedde'sigir therein would not appreciably attack the metal of the screen, s0 that the ultimate etched stencil would retain the screen structure connecting unetche'd portions of the solid sheet. This-requires at-least two che'mically selective metals and critically-see lectiv'e etching. This, in addition to-being criti cal and troublesome, limited the range of etchants and the range of materials availablefor the stencils. An illustration of suchcombinations of metals as used in the prior art would be a stai'n less steel woven mesh with alayer of aluminumor a layer of copper intimately associated there-' with, either by forcing the aluminum intothe interstices of the mesh under great pressure, or by soldering the copper sheetto the screen; or the like.

Itis among the objects of this invention; to

improve stencils; to overcomethe disadvantages of' the prior art; to provide astencil of accuracy and of limited spread of the pigment'ing ri'laterial it'l -passing throughthe-stencil; to provide a meta-1' stencil of strength and accuracy and formed of a single homogeneous metal; to simplifiy themanufacture and-use of metal stenci-1's;. to provide ametal stencil of particular utility in applying designs to objects by meansof radium painter the like; to provide improvements in the: methodof making metal stencils; and many other 0b"- J'ectsand advantages of the invention will be come" more apparent as the description proceeds.

In carrying out the invention in a" preferred embodiment. a selected solid sheet or" plate et metal is" first providedwith a coating offlr'cold' 2. top or the like; a: design is applied thereto photographic process, the plate is then" etched until the design has been etched about one-half way through the sheet. The plate is washed dried, pursuant to which th'efinished' upper'half and the other surfaces of the plate are coated.

with a resist; except for a design area in thelower surface thereof, in which latter a coating of" cold top or thelike-is applied; aseries of half tone dots or the like is photographically applied to the lower surface, then the plate is placed theetching bath and the dots are eaten into the metal until they have gone a distance inwardly sufficient to eat into the surface covered by the resist in the bottom of the previously etched design, and this completes a stencil in which the design area is etched about halfway down froth the top While the screenor mesh is etched about half Way up from the bottom" to penetration of thedesign to'form a transversethroughpign'ierit' transferring channel. Alternatively, both d'e*- signs may be etched simultaneously from spec: site sides of the sheet.

In the accompanying drawing forming part of this description, Fig. 1' represents a fragmentary perspectivepartially broken away showing a: solid sheet of metal fromwhich the' steripil' is made, the coating of cold top or the like by which the initial design is etched, and; progres s'ively the design in fragmentary part etched part way into the upper surfaceof the plate;

Fig. 2- represents a similar fragmentary per: spective of the plate at the completion of the initial etching of the surface and the applica-'-" tion of a resist to the finished ortions of the etched plate. M

Fig. 3 represents asimilar fragmentary per: spective of the complete stencil a's finished by etching half tone dots or the likefrci'n' the-under side of the plate.

Fig. 4 represents" an enlarged fragmentary" perspective of the completed stencil showin the preferred form of complemental dot etchi' Fig. 5 represents" asimilar fragmentary p r spective of a complete stencil showing a modified form of complem'ental dot etching.

I In carrying out the invention in the'preferrecl form; a sheet or plate of metal ['0 is provided which is preferably of strong metal but thin, say; of the order of perhaps fir-Or n .00-1' to .008". Although ordinary-bronze or brass: be u'sed, or sheets o f copper o'r aluminum-orevem compound or composite lei-metallic sheets can be used; it is preferred to use stainless steelf'or beryllium-copper for the stencils. J

After being properly cleaned, this sheet M is:

coated with a coating H of cold top or the like upon its upper surface 9 upon which a photographic impression of the desired stencil design is applied. The rest of the plate being suitably protected as by a coating of resist, not shown, the plate is placed in an etchant bath and the design I2 is etched in the upper surface of the plate. This is carefully timed to insure that the lower etched surface 13 of the design l2 extends only approximately one half way into the plate from the upper surface 9 thereof, although any over-etching or under-etching can be compensated for by the bottom etching time, to be described. This part of the etching may also find that very small elements of the design may take a little longer etching than the large symbols or elements, and it is therefore to be understood that in recognition of this fact, the etching of the large elements will be constantly watched by frequent visual inspections and when completed the plate will be removed from the bath, washed, and dried, and a coating of resist will be applied over the completed large units, then the plate will be returned to the etchant for a further period of etching to insure completion of small units, such as fine printing or the like. At the completion of this step, as indicated at the right side of Fig. 1, the design 12, illustratively including both an etched area designated by the lower surface 13 thereof, which is coextensive over the lower level, so to speak, of the design, and the surface 9 of the plate defining the edge of the design l2 on one side thereof, has an island or raised element l4 on the other side thereof, which is to be blank in the transferred design, but which is supported and held in place across the etched design surface area I3.

The plate completely finished with the design l2 etched into the upper surface S), and possibly having islands l4, depending, of course, on the particular design, as shown in Fig. 2 has a preferably transparent layer of resist l5 applied to the entire upper surface and preferably around the edges of the plate and upon the marginal portion of the lower surface :8 terminating, illustratively, at a line ll on the rear face of the plate 10. In the area defined or framed by the edges ll of the resist I5, a coating of cold top or the like I8 is applied to the lower surface [6. Then photographically, or by some such means, the entire area under the design 12 is treated with a series of dots, such as round dots of standard half-tone processes of printing, or in any other shape or design to the end that the entire area is imparted a mesh-like or analogous impression. Then the photographically treated plate is again immersed in the etchant, and a series of holes are etched in the lower surface It and carefully timed or watched until they have completely eaten into the design lower surfaces l3, a shown in Fig. 3, upon which the etching is terminated, the plate is washed and dried and is ready for use as a metal screen stencil.

As shown in Fig. 4, if, for convenience, a conventional newspaper half-tone is used, there will be formed a series of more or less cylindrical through apertures 26 separated by integral metal portions 21, and in effect forming-a mesh. The thickness of the metal as also the width of metal 2| between apertures 2i] in Fig. 4 is exaggerated, as there is preferably appreciably more hole area than metal, and the metal is very thin, as previously recited, depending upon the requirements and upon of the plate.

the strength of the metal surface and design-piercing apertures, an actual- For many cases, it is preferred to use a redtangular print for the formation of the mesh, so that the photographic design will be such as to create, when etched, a series of rectangular through apertures 22, separated by integral strands or plate elements 23, as shown in Fig. 5, and such construction may well be preferred. Thi is especially true when ultra sharpness of definition of the transferred design is desired.

It is, of course, recognized that by this process there will be a number of blind apertures left in the bottom of the plate running up part way through the plate into the area thereof comprising the unetched top portion, but these make no difference except to furnish a lower surface which seems almost completely a mesh, but the only important part of the mesh is in line or in registration with the etched design l2. In this connection it will be apparent that in place of the half-tone process for forming the lower desired mesh formation or semi-mesh formation, of any desired numbers of apertures can be photographed or projected upon the coating of the lower surface and this mode of formation is part of the invention herein. a

It is an important part of the invention to simplify even the procedure just outlined. According to this improved technique, the thoroughly cleaned plate is coated on both surfaces with the cold top or the like. An exposure is made photographically or the like of the design on the cold top coated surface on one side which is to be transferred. Before subjecting it to the etchant, the exposure is made of the dotted area or half-tone impression on the other cold top coated surface of the plate. Then the plate is immersed in the etchant and both designs are simultaneously etched or eaten into the plate. The process is continued until registration and through apertures have been formed, which will be at a line approximately one-half way through the plate. The etching is then stopped, the plate washed and dried and the stencil is ready foruse.

vention, and the strength and wear resistance of the ultimate stencil formed thereby will be obvious. Having thus described my invention, I claim:,

1. The method of making a metal stencil screen, which comprises coating a plate with photo-sensitive resist material, photographing on one surface a design which the stencil is to reproduce, photographing on the other surfaceof the plate a multiplicity of small dots, subjecting the plate to etchin in a bath to simultaneously etch in the design and a multiplicityof small apertures leading into the design to complete the stencil.

2. The method of making a metal stencil screen which comprises applying to a surface of a plate a photo-sensitive resist, treating the resist so as to enable an etchant to etch a design in the surface on which lies the treated resist, etching the plate and establishing an etched depth transversely overlapping the design etched-f The quickness, ease, and simplicity of the in-- in the opposite surface to establish through apertures in the plate, and in the treatment insuring that one of the said designs comprises a multiplicity of relatively small dots which when etched simulate a screen mesh.

3. The method of making a metal stencil screen, which comprises coating a plate on one surface with photo-sensitive resist material, photographing on said surface a design which the stencil is to reproduce, exposing said surface to an etchant to etch said design into said surface, coating the other surface of the plate with photo-sensitive resist material, photographing said other surface with a multiplicity of dots, exposing said other surface to an etchant having the same qualities as the first to etch said dots into said other surface until the designs overlap and intersect internally of the plate to form through apertures.

4. The method of making a metal stencil screen whch comprises coating the respective sides of the plate with photosensitive resists, photographing designs on the respective sides, one of which is the design to be reproduced and the other of which is such as to impart a meshlike appearance to the plate, subjecting the sides successively to etchants of the same characteristics until there is transverse overlap of the designs internally of the plate to form through apertures for the pigment.

5. The method of making a metal stencil screen from a unitary homogeneous plate, which comprises coating the respective sides of the plate with resist, treating the resist on one face of the plate so as to enable an etchant to etch a design in one face, treating the resist on the other face of said plate to enable an etchant to etch a sec- 0nd design on the latter face, subjecting the faces successively to etchants of the same characteristics until there is a transverse overlap of the etched designs internally of the plate to form through apertures for the pigment, one of said designs comprising a simulation of a screen mesh and the other the design to be printed.

6. The method of making a metal stencil screen from a unitary homogeneous plate, which comprises coating the respective sides of the plate with resist, treating the resist on one face of the plate so as to enable an etchant to etch a design in one face, treating the resist on the other face of said plate to enable an etchant to etch a sec ond design on the latter face, subjecting the faces simultaneously to a common etchant until there is a transverse overlap of the etched designs internally of the plate to form through apertures for the pigment, one of said designs comprising a simulation of a screen mesh and the other the design to be printed.

HARWOOD B. FOWLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 378,423 Baynes Feb. 28, 1888 1,456,794 Gestether May 29, 1920 2,071,249 Cantor Feb. 16, 1937 2,166,367 Norris July 18, 1939 2,217,334 Diggory Oct. 8, 1940 2,340,485 Norris Feb. 1, 1944 2,389,504 Guellich Nov. 20, 1945 2,395,448 Brennan Feb. 26, 1946 

1. THE METHOD OF MAKING A METAL STENCIL SCREEN, WHICH COMPRISES COATING A PLATE WITH PHOTO-SENSITIVE RESIST MATERIAL, PHOTOGRAPHING ON ONE SURFACE A DESIGN WHICH THE STENCIL IS TO REPRODUCE, PHOTOGRAPHING ON THE OTHER SURFACE OF THE PLATE A MULTIPLICITY OF SMALL DOTS, SUBJECTING THE PLATE TO ETCHING IN A BATH TO SIMULTANEOUSLY ETCH IN THE DESIGN AND A MULTIPLICITY OF SMALL APERURES LEADING INTO THE DESIGN TO COMPLETE THE STENCIL. 